1. Magnetic Resonance as a tool for structural studies of membrane proteins
Magnetic Resonance is used to analyze electron absorption or emission of
electromagnetic radiation when a certain magnetic field is applied. Mary Chely Quinones
explained two techniques where magnetic resonance is administered. These are Nuclear
Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR). NMR consists in the
absorption of electromagnetic radiation to determine the structural features of a molecule.
Absorptions are shown as curves. On the other hand, EPR works when elements have an
unpaired electron as is the case with iron. There are two types of interactions. In isotropic
interactions the electrons have no definite direction in the magnetic field and in anisotropic
interactions electrons have a direction in the magnetic field. Researchers observe the magnetic
field at which unpaired electron molecules and ions come into resonance with monochromatic
radiation.
The main purpose for these techniques is to study the structure of proteins identifying
their active site in order to design more efficient drugs. In EPR there is a technique called Spin
Labeling (SLEPR) that is used to study protein mobility, distance, folding, dynamics, and ligand
binding. It consists of introducing nitroxide and stable organic free radicals (the unpaired
electron). SLEPR indicates the mobility of the protein; how fast the molecule moves in the
magnetic field in order to compare it to biological activity. Molecules have positions and it has
been demonstrated that more biological activity occurs in position 5 rather than 16. In graphic
representations it is shown as little curves at the beginning and the faster the molecule moves the
smaller the curves. This helps scientist study the dynamics of molecule,( for best result neutral
labels suggested). Magnetic Resonance serves as a tool for investigating diseases in search of
their cure. MRI is an example of the application of NMR. Electromagnetic Resonance is widely

2. used in the study of proteins in a physiological environment of 25 C°.
At first this theme seemed unexplainable to me. My interest, a more personalized class
discussion during the Journal Club, and the participation of the group helped me understand the
Electromagnetic Resonance topic better. Even though we are not chemistry experts, I now have a
basic idea of some techniques that can be useful to the research community. These investigations
contribute to new findings that will benefit the public in terms of the identification of new
protein structures.
Questions:
1) What is the difference between EPR and MNR?
2) What are radicals and their purpose?
3) Why is EPR useful? Can you mention some examples of applications in the medical field?
4) What is the importance of studying the structures of proteins?